In the past, there have been proposed various types of passive exercise assisting devices which assist a user to stretch ones muscles without effort but with an aid of external forces being applied to the user in order to give an exercise effect. The devices are known to be classified into two types, one being configured to apply a force of bending joints of the user for stretching the muscles associated with the joints, and the other configured to apply a stimulus to a user's body to cause a nervous reflex by which associated muscles are forced to stretch.
Further, the devices are designed to require the user to take different postures depending upon the muscles to be stretched. One example of the devices is to simulate a walking by the user at a standing posture mainly for the purpose of preventing osteoarthritis or walk-training, as proposed in JP 2003-290386 A and JP10-55131 A.
JP 2003-290386 A discloses a trailing device which includes a pair of steps bearing thereon left and right feet of the user, and is configured to interlock the reciprocating movements of the left and right steps for providing a skating simulation exercise to the user. The device is designed to adjust a phase difference of 0 to 360 degrees between the left and right steps with regard to the forward/rearward movements as well as to the lateral movements, and is initially set to have the phase difference of 180 degrees and to vary the phase difference in a direction of increasing a period in which the left and right steps moves forward/rearward together. The steps are driven by a driving mechanism to move so that the user can enjoy the passive exercise simply by placing one's feet on the steps and without making an effort or active movement.
Further, the device of JP 2003-290386 A is arranged to shift the user's weight along forward/rearward direction and also along lateral direction such that the user makes the use of one's nervous reflex to keep a balance with an effect of stretching the muscles. The steps are caused to move substantially in parallel with each other so that the weight of the user shifts simultaneously in the forward/rearward direction and the lateral direction.
The device of JP 10-55131 A is designed for walking training or virtual-reality exercise, and includes a pair of left and right foot plates driven by a horizontal driving unit, and means for rotating the foot plates in left-and-right directions in order to vary their position with respect to the forward/rearward direction as well as to vary their orientation, and also for varying the height and the inclination of the foot plates.